Fused Deposition Modeling (FDM)

FDM is the most common type of additive manufacturing, with more FDM printers installed globally than any other type. Also known as Fused Filament Fabrication (FFF), the FDM additive manufacturing process uses a heated nozzle to melt and extrude thermoplastics, creating one layer at a time. Given the widespread availability of these printers, FDM is often the first experience people have in the 3D printing world. This method has short lead times and low cost per part. Thanks to a variety of material choices and finishing options, FDM is ideal for creating everything from quick prototypes to the final product.

Why use FDM

Fused deposition modeling is often a cost-effective additive manufacturing method. It doesn’t offer the near-isotropic qualities of selective laser sintering, but the 3D printing process is quick and well priced.

Low cost per part: Light and rigid, FDM parts are quick and affordable to manufacture, making them a favorite among manufacturing companies. In fact, FDM is one of the most cost-effective methods of producing custom parts.
Quick turn-around: The universal advantage of additive manufacturing is that the master copy is entirely digital. With no mold or tooling step, production can move directly to printing the first line of parts. For small 3D print runs, expect quick results.
Wide breadth of material options: Each material used in fused deposition modeling is light yet rigid, with its own unique properties. For example, ABS-ESD7 is static-dissipative, while ULTEM™ 1010 is heat-resistant and food contact-certified.

Common applications

Due to the ease of use and widespread availability, there are many applications for fused deposition molding. Thanks to a variety of material choices and finishing options, FDM is ideal for creating everything from quick prototypes to final parts. The quick, versatile 3D printing method plays a key role in many industries including automobiles and children’s toys.

Jigs and fixtures: FDM is ideal for producing hanging jigs and fixtures. With a solid, inflexible exterior and sturdy but hollow interior, FDM parts are practical and reliable without causing undue stress to the surrounding framework.
Prototyping: The wide variety of chemical-resistant, heat-resistant, and biocompatible materials makes FDM ideal for testing new equipment. In addition, the quick turn-around time and low cost per part enables the 3D printing of multiple prototypes in quick succession.
Small, complex parts: When a part is too complex for conventional manufacturing methods, or requires too much post-production detailing, fused deposition modeling provides an opportunity to keep costs down for these complex parts.

Key advantages of FDM

Low cost per part: Fused deposition modeling’s popularity comes from its price per print. If the demands are within the parameters of FDM’s capabilities, it is most likely the right choice for the job.
Lightweight lattice structure: In most cases, FDM parts are printed with solid shells and lattice infills. This keeps the material light while also cutting down on material costs. The lattice infill is designed to support the external structure of the object without adding needless weight.
Quick turn-around for small batches: As FDM parts must be printed one at a time, this process is not suitable for large-scale production. However, when it comes to small batches, FDM is one of the quickest options available.
Familiar materials: Many of the materials used in FDM are commonly used in other processes, so engineers are comfortable with their physical and mechanical properties.
Aerospace certification: ULTEM, a thermoplastic available for FDM, is currently the only additive material certified for use in aircrafts.
Mid-print hardware insertion: With FDM, washers, nuts, bolts, and threaded rods can be inserted mid-build by technicians without any secondary operations.
Print size: FDM printers have large build volumes relative to other additive technologies, so the technology can create bigger parts.

Key consideration and challenges with FDM

Anisotropic qualities: During the 3D printing process, the new layer of molten thermoplastic remelts the surface of the previous layer and enables bonding. As an effect of this process, the bond strength is always somewhat weaker than the base strength of the material, resulting in decreased strength in the Z plane. Consideration by the designer and operator help manage this inherent feature of FDM.
Lower dimensional accuracy: FDM objects are 3D printed layer by layer, causing the material to cool and shrink unevenly. Warping is most common in large flat areas or thin protruding areas. This can be managed and mitigated by controlling temperatures and adherence of the part to the platform, which is standard practice at Fast Radius.
Temporary support structures: While an FDM part is being printed, any overhangs are given additional supports that must be removed in post-processing. Fast Radius prefers using dissolvable support material in order to prevent damage to the finished product.

For an even structure free from warping or anisotropy, consider urethane casting.

Fused deposition modeling design guidelines

An FDM design must include dimensions, layout, materials or material parameters, surface finish, and any specific considerations for the design. You must note the minimum feature size and wall thickness for each material.

Surface finishes for fused deposition modeling

As an additive manufactured product, an FDM object has a surface finish of fine, layered lines. If this texture doesn’t affect the object’s ability to perform its designed function, it can be used as-is. If a specific finish is needed, there are several quality options to achieve this.

Epoxy coating

A transparent or colored layer of epoxy can be applied to the FDM object’s surface for additional resistance to chemicals and fatigue. Epoxy is lightweight and moisture-resistant, making it ideal for lining fixtures in damp settings.

Vapor smoothing

The layer lines unique to additive manufacturing can be polished into a smooth, uniform texture using vapor smoothing. Depending on the material used, the end result varies significantly in opacity.